In Xerography or an electrostatographic process, a uniform electrostatic charge is placed upon a photoreceptor surface. The charged surface is then exposed to a light image of an original to selectively dissipate the charge to form a latent electrostatic image of the original. The latent image is developed by depositing finely divided and charged particles of toner upon the photoreceptor surface. The charged toner being electrostatically attached to the latent electrostatic image areas to create a visible replica of the original. The developed image is then usually transferred from the photoreceptor surface to a final support material, such as paper, and the toner image is fixed thereto to form a permanent record corresponding to the original.
In some Xerographic copiers or printers, a photoreceptor surface is generally arranged to move in an endless path through the various processing stations of the xerographic process. When the photoreceptor surface is reusable, the toner image is then transferred to a final support material, such as paper, and the surface of the photoreceptor is prepared to be used once again for the reproduction of a copy of an original. In this endless path, several stations of corona charging are traversed. These charging stations may involve one or a cluster of dicorotron units.
Several methods are known for applying an electrostatic charge to the photosensitive member such as the use of electron-emitting pins, an electron-emitting grid single corona-charging structures and multiple dicorotron wire assemblies. In recent development of high speed xerographic reproduction machines where copiers can produce at a rate of or in excess of three thousand copies per hour, the need for several reliable dicorotron wire assemblies in order to utilize the full capabilities of the reproduction system are required. Also, with the advent of color copiers where several corona-charging stations are needed, the requirement for dependable dicorotron wire assemblies for depositing an electrostatic charge is essential.
Generally, in electrostatographic or electrostatic copy processes, as above noted, a number of corotrons or dicorotrons are used at various stations around the photoreceptor. For example, the dicorotrons are used at the station that places a uniform charge on the photoreceptor, at a transfer station, at a cleaning station, etc. In today's high speed copiers, it is important that all corotrons (or dicorotrons) are in perfect working order since corotron malfunction can easily render the entire copying process useless. Some high speed copiers, including color copiers, use several dicorotron units, as many as sixteen corotron or dicorotron units are used. Maintaining each corotron unit in perfect working order is essential to the proper functioning of these complex fast color copiers. It is common to use one or several corona-generating device(s) (“corotron” “dicor” or “dicorotron”) for depositing the electrostatic charge at the above-noted stations. Generally, the structure of a dicorotron uses a thin, glass-coated wire mounted between two insulating anchors or end blocks called “insulators or anchors”, which support the wire in a spring tensioned manner in a singular plane. “Anchor(s)” throughout this disclosure and claims will include the terms “insulators”, “insulator anchors” and “insulator”. “Gripper(s)” throughout this disclosure and claims will include the terms “holder” and “clamp”. These insulators or anchors are installed between relatively rigid grippers or holders or clamps that maintain the insulators in place. These insulator gripper inserts are fixed at two opposite ends of a U-shaped dicorotron unit (“housing” or “shells”). The wire or corona-generating electrode is typically a highly conductive elongated wire situated in close proximity to the photoconductive surface to be charged. Often the corona discharge electrode is coated with a dielectric material, such as glass. Since the wire electrode is comprised of a thin outer glass brittle coating, it may be easily damaged. Some handling or cleaning of this electrode often results in fracture of the glass coating, which could cut or injure the user. While cleaning sometimes corrects problems in this corona electrode, it is sometimes necessary to replace the wire due to degradation in the corona performance or even in breakage of the electrode which could occur during the cleaning.
Manual handling of the glass-coated wire is not recommended nor is the use of prying tools, such as screw drivers or rigid prying objects. Extreme care needs to be observed in changing the corona electrodes or wires. As above noted, because of the large number of dicorotrons or wires needed in some copiers, malfunctioning of these wires presents a formidable problem in today's complex copiers.
Another important consideration is the high costs of dicorotron assemblies. The most expensive major component in the dicorotron unit or assembly is the housing or U-shaped shield which in the prior art houses the wire assembly comprised of the wire anchors (insulators), corona wire electrode and grippers. The least expensive major component in the dicorotron unit or assembly is the wire assembly. It makes sense, therefore, for the faulty wire assembly to be removed and replaced rather than the expensive entire dicorotron unit made up of the wire assembly and U-shaped housing.
There are some systems used to remove and replace wire electrodes from the U-shaped housing, such as the method disclosed in U.S. Pat. No. 5,449,906 (Osbourne). In this prior art system, the U-shaped housing has apertures on its end portions adjacent to the electrode anchors or insulators. A prying tool is then inserted into this aperture to pry or dislodge the two end insulators from their original position thereby removing the two insulators and the attached wire electrode. A tool for replacing the removed wire electrode in Osbourne's process includes a plurality of replacement electrodes mounted on a rigid support frame. Replacement is accomplished by pressing this support frame containing a plurality of corona-generating wire assemblies against the empty U-shaped housing (where old wire has been removed) and thereby replacing the removed wire electrode with a new wire electrode. This prior art process requires prying or dislodging the old wire through an aperture and replacing the old wire with a mounting system where a plurality of corona-generating electrode assemblies are removably mounted in a configuration matching that of the original configuration.